A. Field of the Invention
The present invention relates generally to extruded frames for dynamoelectric machines and more specifically to extruded frames having a plurality of arcuate units for encasing an electric motor.
B. Description of the Prior Art
In the field of electric motor design and fabrication, frames for encasing an electric motor stator typically are designed in two overlapping hemicylindrical pieces capable of being produced by conventional extrusion techniques. During assembly of an electric motor, each piece is typically positioned, one at a time, about the wound core of an electric motor stator to form a cylindrical housing. Each piece is then held in place along the axial length of a wound stator by a specially designed clamping device. The two hemicylindrical pieces are then seam welded along an axially extending line of overlap between the two pieces to permanently affix the pieces about the stator.
One problem with two-piece frame design and assembly is that it may sometimes be very difficult to properly assemble each hemicylindrical portion of the frame about a wound core prior to welding to form a cylinder to perfectly fit the particular dimensions of an individual stator. Also, some type of clamping or holding device is always required during the preliminary assembly stage to maintain each hemicylindrical portion about the wound core.
Another problem encountered with conventional two-piece frames fabricated by extrusion techniques is that the maximum size of the frame, and thus the maximum outer diameter of the wound core, is significantly limited by the size of the extrusion die available to produce the frames. When a two-piece frame is used, the cost of extruding larger diameter frames may be prohibitively expensive.
Yet another problem encountered with conventional two-piece frames, and encountered even more frequently in one-piece frames for relatively small electric motors, is that during transportation of the frames from their fabrication to assembly locations, the risk of deformation of the arcuate structure of the frames may be undesirably high. The frames must be perfectly circular when assembled about a wound core. If the frames are undesirably deformed during transportation, it is sometimes necessary to sufficiently heat the frames to permit adjustment of the inner circumferential arc of the frame to reattain the required circularity of the frame.